Technical Field
This invention relates to trailer hitches and, more particularly, to a sliding hitch for fifth wheel trailers.
Prior Art
In contrast with the present invention, a simple, common type of trailer hitch consists of a rigid tongue centered along the longitudinal axis of a trailer and cantilevered forwardly from the trailer to a pivot connection at the rear end of a vehicle, hereinafter referred to as a truck. This pivot connection, a pin or a ball, secures the tongue to the truck but provides a lateral swinging freedom of movement between the truck and the trailer when the truck is turning.
This conventional trailer hitch has several disadvantages. In the first place, a trailer will often sway from one side to the other while it is being towed, as by a truck, and occasionally this swaying can be severe and extremely hazardous. Also, the trailer will not always properly follow when the truck is turning. Also, a truck and a trailer are very difficult to steer during backing operations. The disadvantages above noted reside primarily in the fact that the tongue of the trailer is connected to the rear end of the truck, usually adjacent to the rear bumper and this connection is several feet behind the rear wheels of the truck. Thus, whenever the vehicle commences to turn in one direction, the first movement at the rear end of the truck is in the opposite direction because, in a relative sense, the vehicle will pivot at its rear axle. This produces, first, a lateral movement away from the turn, and such a movement may be magnified when transmitted to the tongue of the trailer. Swaying of the trailer can thus occur when a truck is driving down a road where the operator has to make minor steering corrections. Each time the operator makes a slight turn to the right or left, the first response by the trailer will be a slight turn in the opposite direction. The trailer will then swing back and overcompensate such movement to produce the resulting side sway in a trailer. The same type of overcompensation occurs when the trailer is being backed up and the operator must learn to control steering movements in the truck that are the opposite from that which would appear to be normal to him.
In commercial tractor-trailer rigs, this problem is obviated by the use of a fifth wheel at the front end of the trailer. This fifth wheel, the pivot connection, is over the rear wheel assembly of the tractor so that the turning of the tractor does not create any significant lateral movement of the trailer. The advantage of such an arrangement has been recognized in small trailers that are towed by pickup trucks, because the trailers for pickup trucks are now being provided with gooseneck connections, a forwardly extended arm which carries an overhanging, forwardly extended connection to produce an equivalent to the fifth wheel. This gooseneck connection connects with a base pad in the bed of the pickup truck directly over the rear axle. The same comparable result is attempted for connecting a trailer to automobiles by using a special tongue connector that extends underneath the rear of the automobile to the rear axle where it is pivoted.
Unfortunately, the conventional gooseneck connectors are not entirely satisfactory. They do transfer a portion of the load on a trailer directly over the drive wheels of a truck, which is desirable, but whenever the truck is pulling a load, the connector on the deck of the pickup truck creates an undesirable torque action tending to lift the steering wheels of the truck and placing excessive stress on the base pad and connector. This causes bucking and sudden forces to be transmitted through the truck cab, resulting in a rough and uncomfortable ride. In addition, this stress can lead to metal fatigue in the base pad and connector.
Accordingly, there is a need for an improved mode of connecting a trailer to a vehicle that will avoid the disadvantages above noted.